1. Field of the Invention
The present invention relates generally to non-volatile semiconductor memory devices and methods of fabricating the same and particularly to non-volatile semiconductor memory devices capable of providing improved electrical characteristics and methods of fabricating the same.
2. Description of the Background Art
Conventionally as one example of semiconductor devices non-volatile semiconductor memory devices have been known (see Japanese Patent Laying-Open No. 8-64700 for example).
Japanese Patent Laying-Open No. 8-64700 discloses in FIG. 3 a non-volatile semiconductor memory device including a semiconductor substrate having a main surface with predeterminedly spaced device isolating trenches internally provided with CVD oxide film forming an isolation oxide film. Between such isolation oxide films on the substrate's main surface a floating gate electrode is disposed with a tunnel oxide film posed therebetween. On the floating gate electrode a control gate electrode is disposed with an ONO film posed therebetween.
In the above conventional non-volatile semiconductor memory device, however, the floating gate electrode has an upper surface having a protrusion and a depression reflecting a feature underlying the floating gate electrode. As such at the protrusion of the floating gate electrode (e.g., an end of the floating gate electrode) the ONO film can differ in thickness, quality and the like from the remainder or electric field concentration can occur. This results in the device having impaired electrical characteristics.